Method for depositing a film using a charged particle beam, method for performing selective etching using the same, and charged particle beam equipment therefor

ABSTRACT

Certain film deposition and selective etching technology may involve scanning of a charged particle beam along with a deposition gas and etching gas, respectively. In conventional methods, unfortunately, the deposition rate or the selective ratio is oftentimes decreased depending on optical system setting, scan spacing, dwell time, loop time, substrate, etc. Accordingly, an apparatus is provided for finding an optical system setting, a dwell time, and a scan spacing. These parameters are found to realize the optimal scanning method of the charged particle beam from the loop time dependence of the deposition rate or etching rate. This deposition rate or etching rate are measurements stored in advance for a desired irradiation region where film deposition or selective etching should be performed. The apparatus displays a result of its judgment on a display device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of nonprovisional U.S. applicationSer. No. 11/808,783 filed Jun. 13, 2007, which is a Continuation ofnonprovisional U.S. application Ser. No. 10/873,170 filed on Jun. 23,2004. Priority is claimed based on U.S. application Ser. No. 11/808,783filed Jun. 13, 2007, which claims the priority of U.S. application Ser.No. 10/873,170 filed on Jun. 23, 2004, which claims the priority ofJapanese Application 2003-336691 filed on Sep. 29, 2003, all of which isincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for depositing a film by using adeposition gas, a method of selective etching by using an etching gas,charged particle beam equipment for these methods, a method formanufacturing a large scale integration (LSI), and a technology of LSImanufacturing equipment. More particularly, the present inventionrelates to technology that is effective when being applied to a methodfor depositing a film by using a deposition gas and a focused ion beam(FIB) or a method for performing selective etching by using an etchinggas and a FIB.

2. Discussion of Background

A conventional FIB apparatus can scan the surface of a sample with theFIB, detect secondary electrons and secondary ions generated from thesample surface, and observe a minute region of the sample surface fromtheir profiles. Moreover, the FIB apparatus can perform sputter etchingon the sample surface by scanning the sample surface with the FIB.Furthermore, by introducing a gas used for making a thin film into asample chamber, spraying it on the sample surface, and simultaneouslyscanning the sample surface with the FIB, the apparatus can decomposethis raw material gas and form a metal film, among other things, bydeposition on the sample surface in an FIB scanning region. This filmdeposition method is called the FIB assisted deposition (FIBAD) method.In addition, when performing sputter etching, if an etching gas issprayed on the substrate, the etching rate for each substrateconstituent material can be increased or decreased as desired. Thisetching method is called the selective etching method. The FIBAD methodand the selective etching method are widely used.

FIG. 1 is a view showing FIB scanning and a method for introducing a gasused in the FIBAD method and in the selective etching method. A gas isintroduced to a substrate 21 locally from a nozzle 12. By bringing thenozzle 12 close to an FIB irradiation position, the quantity of gasadsorbed by the substrate 8 can be increased. In the FIBAD method and inthe selective etching method, a gas used as a raw material (depositiongas or etching gas) is sprayed from the nozzle 12, and the FIB isscanned in a desired scanning region 18.

FIG. 2 shows a method for scanning FIB 11. The FIB 11 has a limitedprobe size 14 on the surface of the substrate 8. The deposition gas 15introduced from the nozzle 12 is adsorbed on the surface of thesubstrate 8. The FIB 11 stays at a scan lattice point 16 for a constanttime, and then moves to the adjacent scan lattice point 16 away from thescan lattice point 16 by the distance of a scan spacing 17. Generally,the scan spacing 17 is set in conformity to the probe size 14 of theFIB, that is, to 10 nm to 1000 nm. Repeated scanning of the scanningregion 18 by the above-mentioned technique makes the irradiation densityof the FIB uniform, and simultaneously realizes uniformity of the filmthickness that is formed by deposition in the FIBAD method or uniformityof etching depth in the selective etching method.

As a technology of equalizing the thickness of a film formed by theFIBAD method, there are the following prior arts. A first example (JP-ANo. 298243/1996) discloses a FIBAD method for effectively equalizing thewhole quantity of FIB irradiation on the sample surface in the casewhere there is inclination or holes on the whole surface of a sample onwhich a film is intended to be accumulated by changing the quantity ofFIB irradiation according to an effective area irradiated with the FIB.A second example (JP-A No. 289133/1991) discloses a technology ofequalizing the thickness of a film that is accumulated by controllingscanning conditions of a beam (beam scanning speed, scanning pitch, andscanning pattern) according to beam conditions of the FIB (accelerationvoltage and beam current).

Further, as a technology of equalizing the etching rate in the casewhere selective etching is performed using the FIB, there are thefollowing prior arts. A third example (JP-A No. 120153/1997) discloses atechnology of moving the FIB irradiation spot to the outside of thescanning region and halting the FIB irradiation for a predetermined timeuntil sufficient etching gas is supplied to the adjacent irradiationspot when the FIB irradiation spot is moved to the adjacent irradiationspot. During this period, the FIB is blanked, and hence is not allowedto irradiate a moved position of the beam spot. Because of this, theetching rates in the irradiation spot and in a superposed position areequalized. A fourth example (JP-A No. 29201/2000) discloses a technologyin which the etching rate have been obtained in advance for differentkinds of processing parts (area, position, and shape) and the number ofshots of FIB irradiation is decided according to a processing part.

SUMMARY OF THE INVENTION

It has been recognized that what is needed is *****. Broadly speaking,the present invention fills these needs by providing *****. It should beappreciated that the present invention can be implemented in numerousways, including as a process, an apparatus, a system, a device or amethod. Several inventive embodiments of the present invention aredescribed below.

When film deposition or selective etching is performed using theconventional FIB apparatus, an operator sets a region in which the FIBis scanned and then selects an optimal beam current and a scanningmethod by experience. Moreover, generally the feed rate of a rawmaterial gas and the scanning speed of the FIB at the time of processingare fixed. Unfortunately, if the setup by the operator is improper, afilm is not formed on the substrate surface at the time of filmdeposition, and the etching rate difference on the substrate surfacewithin the irradiation region of the FIB is small at the time ofselective etching. The technology disclosed by the first example aboveis a technology of varying the quantity of FIB irradiation according toan irradiation position. However, mere change in the quantity of FIBirradiation cannot lead to equalization of the deposited film, andconsequently the technology is not able to cope with the deposition rateand the formation of a uniform film simultaneously. The second examplediscloses a technology of automatically setting the beam scanning speed,the scanning pitch, and the scanning pattern according to beamconditions. However, it does not indicate at all how the optical systemsetting should be optimized for a desired scanning region. Thetechnology disclosed by the third example makes it possible to performselective etching with a large selection ratio. However, since movementof the beam spot is delayed until an etching gas is supplied, theprocessing time is increased after all. The fourth example discloses atechnology of deciding the number of shots of FIB irradiation accordingto a processing part considering an etching rate that was found inadvance. However, mere change in the quantity of FIB irradiationaccording to area, position, and shape is insufficient to improve theprocessing speed. This is because if the processing conditions areintended to be optimized, not only the quantity of FIB irradiation butalso the beam conditions of the FIB need to be altered according to aprocessing part, and the alteration of the beam conditions varies theetching rate.

Accordingly, one object of the present invention is to provide chargedparticle equipment capable of forming a film in a desired scanningregion more efficiently than the conventional method in the filmdepositing technology by the use of scanning of a focused chargedparticle beam, or charged particle equipment capable of selectiveetching in a desired scanning region more efficiently than theconventional method in the selective etching technology by the use ofscanning of a focused charged particle beam.

The processing using the FIB (for example, film deposition, selectiveetching, etc.) requires an operation of optimizing a lot of parameters.Among processing parameters of the FIB, the film growth rate at the timeof film deposition and the etching rate have optimal values for a looptime of the FIB. Here, the loop time means a time required for a chargedparticle beam to move from a scanning start position to a scanning endposition and further return to the scanning start position in a desiredregion.

Conventionally, it has been considered that the film growth rate oretching rate only decreases monotonously with increasing loop time, andnot considered at all that it might achieve a maximum or a localmaximum. This concept is reasonable because enlarging the loop timemeans slowing the beam scanning speed, assuming that the area of thescanning region is set constant and the feed rate of a processing gas isset constant, and once the beam scanning speed becomes lower, naturallythe processing speed in the whole processed area decreases.

This invention solves the above-mentioned problem by optimizingprocessing parameters of each FIB in light of the loop time dependenceof the processing speed. By depositing a film according to the scanningmethod and an irradiation density both of which are based on theabove-mentioned setup, a desired film can be formed at high speed, andat the same time the operator can alter the deposition setting inconformity to a desired film quality by reference to display of ajudgment result. Consequently, this method can provide a technology offorming a film efficiently in the film-deposition technology by means ofscanning of a charged particle beam.

The invention encompasses other embodiments of a method, an apparatus,and a system, which are configured as set forth above and with otherfeatures and alternatives.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings. Tofacilitate this description, like reference numerals designate likestructural elements.

FIG. 1 is a view showing a conventional FIB scanning and a conventionalmethod for introducing a gas;

FIG. 2 is a view showing a conventional method for scanning the FIB inthe conventional technology;

FIG. 3 is a view showing an example of arrangement of scan latticepoints in the scanning region, in accordance with an embodiment of thepresent invention;

FIG. 4 is a diagram showing the scan spacing dependence of thedeposition rate, in accordance with an embodiment of the presentinvention;

FIG. 5 is a diagram showing the dwell time dependence of the depositionrate, in accordance with an embodiment of the present invention;

FIG. 6 is a diagram showing the loop time dependence of the depositionrate, in accordance with an embodiment of the present invention;

FIG. 7 is a diagram showing the loop time dependence of the depositionrate of tungsten deposition, in accordance with an embodiment of thepresent invention;

FIG. 8 is a diagram showing the Y_(SP)/Y₀ dependence of the gas looptime Pd that produces the fastest deposition rate, in accordance with anembodiment of the present invention;

FIG. 9 is a diagram showing the beam current that produces the fastestdeposition rate for the scanning area in a certain optical system, inaccordance with an embodiment of the present invention;

FIG. 10 is a schematic view showing the basic configuration of thecharged particle beam equipment, in accordance with an embodiment of thepresent invention;

FIG. 11 is a view showing a scanning region setup screen, in accordancewith an embodiment of the present invention;

FIG. 12 is a view showing a selection screen for optical system setting,in accordance with an embodiment of the present invention;

FIG. 13 is a view showing a deposition-rate calibration screen, inaccordance with an embodiment of the present invention;

FIG. 14 is a view showing the screen on which the deposition rate iscalibrated, in accordance with an embodiment of the present invention;

FIG. 15 is a flowchart showing the film deposition method, in accordancewith an embodiment of the present invention;

FIG. 16 is a view showing the deposition-rate calibration screen, inaccordance with an embodiment of the present invention;

FIG. 17 is a flowchart of an automatic calibration function, inaccordance with an embodiment of the present invention;

FIG. 18 is a diagram showing the cross section of a deposition film, inaccordance with an embodiment of the present invention;

FIG. 19 is a diagram showing the dwell time dependence of the sputterdepth between film and substrate, in accordance with an embodiment ofthe present invention;

FIG. 20 is a view showing one set of film deposition monitor screen ofcontrol systems enabling selection of film quality, in accordance withan embodiment of the present invention;

FIG. 21 is a flowchart of the film deposition method that makes possibleselection of film quality, in accordance with an embodiment of thepresent invention;

FIG. 22 is a configuration example of the charged particle beamequipment, in accordance with an embodiment of the present invention;

FIG. 23 a part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 b part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 c part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 d part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 e part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 f part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 g part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 h part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 i part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 23 j part of a set of illustrations showing a sample fabricationmethod that uses the FIB apparatus, in accordance with an embodiment ofthe present invention;

FIG. 24 is a view showing is one set of deposition monitor screen ofcontrol systems, in accordance with an embodiment of the presentinvention;

FIG. 25 is diagrams showing the loop time dependence of the etching rateand that of the etching rate difference, in accordance with anembodiment of the present invention;

FIG. 26 is a view showing one set of selective etching monitor screen ofcontrol systems, in accordance with an embodiment of the presentinvention; and

FIG. 27 is a flowchart showing the selective etching method, inaccordance with an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An invention for ***** is disclosed. Numerous specific details are setforth in order to provide a thorough understanding of the presentinvention. It will be understood, however, to one skilled in the art,that the present invention may be practiced with other specific details.

First Embodiment

FIG. 3 shows schematically how a beam spot of a charged particle beammoves in the scanning region, in accordance with an embodiment of thepresent invention. One circle corresponds to one beam spot, and the beamspot is scanned along the direction of the arrow. Here, the “beam spot”means the size of an area in the sample surface that is occupied by thecharged particle beam incident thereon. The center of the beam spot iscalled a “scan lattice point,” and is designated by the numeral 16 inFIG. 3. The numeral 18 denotes a scanning region, and FIG. 3 shows anexample in which the scan lattice points are arranged to form triangularlattices in the scanning region.

FIG. 4 shows the scan spacing dependence of the deposition rate, inaccordance with an embodiment of the present invention. Here, the “scanspacing” means a distance between a certain scan lattice point and ascan lattice point most adjacent to the scan lattice point, and the“deposition rate” is the growth rate of a film thickness per unit time.The dwell time during which an incident charged particle beam stays atone beam spot and the loop time were fixed. The deposition rateincreases with increasing scan spacing up to a distance of Point d, andafter taking the maximum value at Point d, decreases with increasingscan spacing. The numeral 14 in the figure represents Point d. The sizeof Point d is equal to the magnitude of the probe size. In a range wherethe scan spacing is smaller than a distance of Point d, this signifiesthat the scan spacing is smaller than the beam spot size. In this range,when the beam moves to the adjacent spot, the beam in the adjacent spotoverlaps the previous beam in the spot before moving in the saidpositions, where supplied deposition gas molecules are entirelyconsumed, and the deposition rate decreases.

Accordingly, as the scan spacing becomes smaller, an area defined bypositions of superposition increases, and the deposition rate decreases.In a range where the scan spacing is larger than a distance of Point d,there develops a gap between adjacent beam spots. Since the beam is notmade to irradiate the gap, an area where a film is not formed isproduced in the scanning region, and consequently the deposition rateaveraged in the whole scanning region decreases. For this reason, thedeposition rate decreases with increasing scan spacing. A state wherethe scan spacing is equal to the probe size is identical to a statewhere the gap between adjacent beam spots is zero.

FIG. 5 shows the dwell time dependence of the deposition rate, inaccordance with an embodiment of the present invention. Here, the “dwelltime” is a time during which the beam spot stays in a certain position.The scan spacing is adjusted to agree with the probe size so that a gapdoses not develop between the adjacent beam spots. The loop time and thefeed rate of the gas were fixed. The deposition rate increases withincreasing dwell time, taking the maximum value at the optimal dwelltime Td. When the dwell time passes the optimal dwell time, thedeposition rate decreases with increasing dwell time. This signifiesthat when the feed rate of the processing gas to the processed regionand the dwell time in the processed region take the optimal values, theprocessing speed becomes the maximum.

FIG. 6 shows the loop time dependence of the deposition rate. The dottedline is the loop time dependence of the deposition rate consideredconventionally, and the solid line shows the loop time dependence of thedeposition rate in this embodiment. The scan spacing was fitted to theprobe size d, and the dwell time was fixed to the optimal dwell time Td.In the dotted line, the deposition rate reduces monotonously withincreasing loop time, whereas in the solid line, the deposition ratetakes the maximum value at loop time of Pd and decreases as the looptime leaves Pd.

FIG. 4, FIG. 5, and FIG. 6 show that the deposition rate becomes themaximum with the following setup: the scan spacing is set to the probesize d; the dwell time is set to the optimal dwell time Td; and furtherthe size of the loop time is set to Pd. That is, in order to maximizethe deposition rate, it is necessary to set the three parameters, scanspacing, dwell time, and loop time, to the optimal values. Both theprobe size d that is the optimal value of the dwell time and the optimaldwell time Td that is the optimal value of the dwell time are stronglydependent on the optical system setting, especially on the beam currentdensity of the charged particle beam. Note that the probe size d tendsto increase in proportion to the beam current density. Therefore, theoptimal dwell time is in inverse proportion to the beam current density.That is, designating the scanning area that maximizes the depositionrate for each optical system setting by S, S can be expressed roughly bythe expression S=Pd×d²/Td.

Next, by way of example, for a case where tungsten is used as adeposition material, how to obtain the relationship between the scanningarea maximizing the deposition rate and each optical system setting willbe illustrated.

FIG. 7 shows the loop time dependence of the deposition yield fortungsten deposition, in accordance with an embodiment of the presentinvention. The deposition rate decreases for the loop time of 1 ms orless because it takes a time of about 1 ms for gas molecules to beadsorbed again on the substrate to become a sufficient quantity afterbeing consumed by the FIB. On the other hand, the dwell time is a valueof the order of μsec. It takes a time longer than the dwell time for thesubstrate to adsorb a sufficient amount of gas molecules.

The loop time dependence of the deposition rate shown in FIG. 7 can befitted using the following empirical formulas for the deposition rate Y.

Y=Y ₀(1−e ^(−P/t))−Y _(SP)  (1)

Here, Y₀ is a deposition coefficient; P is loop time 23; τ is arelaxation time; and Y_(SP) is a sputter coefficient. Physically, thefirst term of Equation 1 represents the rate of the film thickness thatis being formed and the second term Y_(SP) represents the rate of thefilm thickness that is being etched by the sputtering. In order to findvalues of the parameters that fit Equation 1, all that is necessary isto find measured values of deposition rates for three points, Point A34, Point B 35, and Point C 36, or so. The deposition rate W is obtainedfrom Equation 1 as follows:

$\begin{matrix}{W = \frac{Y \cdot {Ip} \cdot {Td}}{P \cdot d^{2}}} & (2)\end{matrix}$

Here, Ip is the beam current; Td is the optimal dwell time; P is theloop time; and d is the probe size. The maximum value of W for differentloop time is obtained when the differential coefficient of W at P=Pdequals to zero, which is expressed by the following Equation 3:

$\begin{matrix}{{\frac{W}{P}_{P - {Pd}}} = 0} & (3)\end{matrix}$

Here, Pd is the gas loop time. FIG. 8 shows the Y_(SP)/Y₀ dependence ofthe Pd/τ obtained from Equation 3. Pd, which is in inverse proportion toτ, increases with increasing Y_(SP)/Y₀. Thus, Pd can be decided from theloop time dependence of the deposition rate.

FIG. 9 is a diagram showing the relationship between the beam currentthat produces the fastest deposition rate and the scanning area in theadopted optical system of the FIB equipment, in accordance with anembodiment of the present invention. The vertical axis represents thebeam current, and the horizontal axis represents the scanning area atwhich the deposition rate becomes the maximum for each optical systemsetting. The scanning area in which the deposition rate becomes themaximum was obtained by an expression S=Pd×d²/Td. The parameter Pd inthe expression of S can be calculated by finding Y₀, τ, and Y_(SP) fromthe fitting curve in FIG. 7 and substituting them into the solid line inFIG. 8. The parameter Td in the expression of S is the dwell time atwhich the solid line in FIG. 5 takes a peak value.

Moreover, the parameter d in the expression of S is a scan spacing atwhich the solid line in FIG. 4 takes a peak value. This scan spacing isin agreement with the probe size that varies depending on the beamcurrent. Only after substituting the probe size of each beam current forthe parameter d in the expression of S and comparing S, it becomespossible to decide the beam current that produces the fastest depositionrate for each scanning area.

The following discussion provides a summary of the method for decidingdeposition parameters described above. The proposed method is a methodfor depositing a film on a sample substrate by spraying a deposition gason the sample substrate and further scanning a charged particle beamthat is focused by a charged-particle-beam irradiation optical system.The deposition rate is estimated from information of the loop timedependence of the deposition rate. The scanning is performed whileholding the scan spacing and the dwell time of the charged particle beamconstant.

In addition, the proposed method is this film deposition method, whereinfilm deposition is done by the following steps: storing the beamcurrent, the probe size, and the optimal dwell time for each opticalsystem setting; storing the loop time dependence of the deposition ratefor each optical system setting in the form of a table or in theEquation 1; finding the deposition rate for an arbitrary scanning regionby at least Equation 2; selecting an optical system setting thatmaximizes the deposition rate based at least on FIG. 9; and depositing afilm using a scan spacing and an optimal dwell time that are obtained bythe selected optical system setting and the probe size.

By incorporating the sequence described above into a sequencer of thedeposition equipment or by incorporating it into a control unit of thedeposition equipment as software, deposition equipment capable ofprocessing with the deposition rate being set to the fastest to atargeted scanning area can be provided. The scanning area is inputtedthrough a user interface of the deposition equipment. Note that thismethod is also applicable to selective etching using an etching gas, aswith the film deposition using a deposition gas.

FIG. 10 shows a configuration example of the charged particle beamequipment that realizes the film deposition method described in thisembodiment, in accordance with an embodiment of the present invention.The charged particle beam equipment in FIG. 10 comprises the following:a charged particle beam apparatus that extracts an ion beam from an ionsource 1 by an extraction electrode 2, focuses the ion beam with acondenser lens 3, subsequently narrows the ion beam with a beamrestraining aperture 4, and focuses the ion beam on the surface of asample 8 with an objective lens 6; a movable sample stage 7 for mountinga sample; a secondary particle detector 9; a deflector 5; a control unit10; a deposition gas nozzle 12.

FIG. 11 is a monitor screen of control system that serves as the userinterface for controlling the deposition equipment shown in FIG. 10. InFIG. 11, a screen for setting up a scanning region is displayed on themonitor screen of control system. The operator sets the scanning region31 in which a film is intended to be deposited, by referring to ascanning ion microscope image (SIM image) 30. The setup of the scanningregion 31 is done through inputting means, such as a keyboard shown inthe control unit 10 in FIG. 10. The control unit 10 of the depositionequipment locates the scanning area 19 from the preset value of theinputted scanning region 31, then finds the beam current 32 thatproduces the fastest deposition rate for the scanning area 19, anddisplays it on the monitor screen of control system. This scanningregion setup screen displays the optimal values of the depositionparameters (beam current, dwell time, scan spacing, etc.) for theinputted scanning region 31.

FIG. 12 is an example of the control screen for optical system settingselection displayed on the monitor screen of control system. The controlunit 10 of the deposition equipment finds the deposition rates for twoor more beam current values responding to values of the scanning regionbeing set through the user interface, and displays them on the selectionscreen for optical system setting. The deposition rate to be displayedmay be calculated each time, or a value stored in the control unit or anexternal storage means may be read and displayed. The equipment operatorselects the beam current value that produces a desired deposition ratethrough the user interface; the deposition equipment performs depositionunder optimal conditions according to the inputted beam current value.The selection screen for optical system setting could display thedeposition time instead of the deposition rate. Incidentally, it is alsopossible to set the beam mode as a choice other than the beam currentvalue and display it on the selection screen for optical system setting.

Second Embodiment

In the first embodiment, the optimal values of the depositionparameters, Pd, Td, and d, were found by using the parameters decidedfrom the fitting curves shown in FIGS. 7 through 9. The fitting curvesshown in FIGS. 7 though 9 are curves that can be used for yearsfundamentally once they have been decided. However, there is a casewhere the fitting curve itself needs to be calibrated due to individualdifference of equipment at the time of shipping, variation in depositionconditions, etc. Accordingly, in this embodiment, the fitting curves anda method for calibrating deposition parameters decided by the said curvewill be described.

FIG. 13 shows the deposition-rate calibration screen that is displayedon a user interface screen of the control unit 10 included in thedeposition equipment, in accordance with an embodiment of the presentinvention. The process and material 37 and the beam current 39 can beselected, individually. Here, the process means the kind of processing;in this embodiment, the process is selected from two kinds: filmdeposition (deposition), and selective etching. FIG. 13A shows a casewith the following selections: the process is deposition; the depositionmaterial is tungsten; and the beam current 39 is 1.00 nA. The probe sized is inputted as a scan spacing 40, the optimal dwell time 26 isinputted as a dwell time 41, and measured values of the film thicknessobtained for different loop times are inputted as Point A 34, Point B35, and Point C 36. According to the measured values of the filmthickness being inputted, Pd/τ, Y_(SP)/Y₀, etc., which are fittingparameters of the fitting curve, are calculated again and stored in thestoring means in the control unit 10. The monitor screen of controlsystem may be configured to show a plurality of calibration screens.FIG. 13B shows a calibration screen in the case where selected values ofthe optical system 39 are changed and fitting parameters are calibrated.Each time the selected values of the process and material 37 and theoptical system setting 39 are changed, the probe size 14, the optimaldwell time 26, the film thicknesses measured for respective loop timesare inputted as entries of the scan spacing 40, the dwell time 41, PointA 34, Point B 35, and Point C 36, respectively.

In FIG. 13, the calculation of the fitting parameters is done by thecontrol unit of the deposition equipment, but the operator may input thefitting parameters directly. FIG. 14 shows the screen used forcalibrating the deposition rate. For each process and material 37 andeach preset value 39 of the optical system, the probe size d, theoptimal dwell time Td, the deposition coefficient obtained from the looptime dependence of the deposition rate, the relaxation time, and thesputter coefficient are inputted as entries of the scan spacing 40, thedwell time 41, Y₀, τ, Y_(SP), respectively. The calibrated depositionrate is stored in the control unit 10 included in the depositionequipment, and is used to display the selection screen for opticalsystem setting shown in FIG. 11 or FIG. 12.

FIG. 15 is a flowchart showing a method for depositing a film, inaccordance with an embodiment of the present invention. By thecalibrating means for calibrating the deposition rate shown in FIG. 13or FIG. 14, the probe size d, the optimal dwell time Td, the depositioncoefficient Y₀, the relaxation time τ, the sputter coefficient Y_(SP),and the optimal loop time Pd are set for two or more beam current valuesand are stored in the storing means in the control unit 10. In thisoccasion, a method in which the scanning area and the deposition rateare stored in the form of a table for each beam current value assubstitutes for the deposition coefficient Y₀, the relaxation time τ,the sputter coefficient Y_(SP), the optimal loop time Pd, etc., may beused. In each optical system setting, the scanning area S that realizesthe fastest deposition rate is expressed by Equation 4:

$\begin{matrix}{S = \frac{{Pd} \cdot d^{2}}{Td}} & (4)\end{matrix}$

The control unit 10 selects an optical system setting that has ascanning area S close to the preset value of the scanning area being setthrough the user interface. Thereby, deposition parameters, such as beamcurrent, dwell time, and scan spacing, are set automatically.Alternatively, since the probe size d affects the deposition rate, thefollowing procedure may be adopted: auto-focusing is executed beforefilm deposition; and the probe size d is set so that the beam is infocus on the surface of a sample that is at work. Furthermore, thismethod can also shorten the deposition time compared with theconventional method.

FIG. 16 shows the deposition-rate calibration screen, in accordance withan embodiment of the present invention. The means for calibrating thedeposition rate described above is supplemented with an automaticcalibration function 45 of estimating values of the depositionparameters at a different beam current value from preset values of thedeposition parameters at a selected beam current value.

FIG. 17 is a flowchart in the case where the automatic calibrationfunction is added, in accordance with an embodiment of the presentinvention. The relaxation time and the deposition coefficient are foundusing the measured value of the deposition rate for one optical systemsetting. The relaxation time and the deposition coefficient for anotheroptical system setting are derived using their variations.

Third Embodiment

When a film is deposited by the FIB, there may be a case where a hollowis formed underneath a region where deposition is performed. This hollowis not a cavity in which nothing exists. Rather, the hollow formed isembedded with either a material whose material composition is the sameas a film to be deposited or a reaction product of a material of thefilm to be deposited and a material forming the processed region. Thereason for this embedded hollow is because the processed region ispartly removed by a sputtering effect before the film is accumulated bythe FIB and then the film is accumulated on it.

FIG. 18 shows how this process proceeds with a diagram showing the crosssection of a deposition film, in accordance with an embodiment of thepresent invention. At a junction plane between the substrate 8 and thedeposition film 13, a hollow is formed on the substrate surface by theFIB. When film deposition is done with Ga ions of 30 keV, the sputterdepth between film and substrate 61 may become as much as 200 nm.

FIG. 19 shows the dwell time dependence of the sputter depth betweenfilm and substrate, in accordance with an embodiment of the presentinvention. The sputter depth between film and substrate takes roughly aconstant value for the dwell time ranging from 0 to the optimal dwelltime Td, but increases for the dwell time exceeding Td. If the dwelltime, among the deposition parameters, is set to the optimal dwell timeTd and a film is deposited, the sputter depth between film and substratecan be made shallow as compared to a case of the film deposition thatuses conventional technology.

FIG. 20 is one set of deposition monitor screen of controlling systemsenabling selection of film quality, in accordance with an embodiment ofthe present invention. In the selection screen for optical systemsetting in FIG. 12, the sputter depth between film and substrate and theprobe size are newly displayed. The operator can select a film qualityfrom the sputter depth between film and substrate and the probe size.The registration screen is the registration screen in FIG. 13 with thesputter depth between film and substrate added.

FIG. 21 is a flowchart of the film deposition method that makes possibleselection of film quality, in accordance with an embodiment of thepresent invention. The means for calibrating the deposition rate in FIG.21 is the means for calibrating the deposition rate in FIG. 15 with theregistration of the sputter depth between film and substrate (δW) 46added. The optical system setting is altered from “Decide” to“Candidates of optical system setting are displayed” so that theoperator can select it considering the film quality. The flowchart shownin FIG. 21 is incorporated in the control unit of the depositionequipment as software, and the control unit makes the depositionapparatus operate according to the steps shown in the flowchart.

Fourth Embodiment

FIG. 22 is a configuration example of the charged particle beamequipment, in accordance with an embodiment of the present invention.The charged particle beam equipment in FIG. 22 comprises: a chargedparticle beam apparatus that extracts an ion beam from an ion source 1by an extraction electrode 2, focuses the ion beam 11 with the condenserlens 3, subsequently narrows the ion beam with the beam restrainingaperture 4, and focuses the ion beam 11 on the surface of the sample 8with the objective lens 6; movable sample stage 7 for mounting a sample;the secondary particle detector 9; the deflector 5; the control unit 10;the deposition gas nozzle 12; and a mechanical probe 13.

FIG. 23 shows one example of a method for preparing a sample using anFIB apparatus, in accordance with an embodiment of the presentinvention. In this technique, a substrate 51 is maintained at anattitude so that the ion beam 52 irradiates the surface of the samplesubstrate 51 at a right angle; the ion beam 52 is made to scan in thevicinity of an observation region 50 so as to draw a rectangle, wherebya square hole 54 of a necessary depth is formed in the sample surface(FIG. 23 a). Next, a slot 55 is formed in the sample surface by scanningthe ion beam 52 to draw a rectangle (FIG. 23 b). Next, the substrate 51is inclined so that the axis of the ion beam 52 forms a tilt angle ofabout 30° with a normal of the surface of the substrate 51 and a slantslot 56 is formed. A change in attitude of the substrate 51 for the tiltangle is done by the sample stage (FIG. 23 c). A tip of the mechanicalprobe 53 is contacted to a part of the substrate 51 that will become asample (FIG. 23 d). A deposition film of a protective film 57 is formedby supplying a deposition gas from a deposition gas nozzle 20 and makingthe ion beam 52 irradiate locally a region that includes a tip part ofthe mechanical probe 53. A specimen 58 that is a separated portion ofthe substrate 51 and the tip of the mechanical probe 53 that are in acontact state are connected with a deposition film for probe fixing 57(FIG. 23 e). A remaining part is subjected to cut-off processing by theFIB, and the separated specimen 58 is cut off from the substrate 51. Theseparated specimen 58 thus cut off becomes a state of being supported bythe mechanical probe 53 connected thereto (FIG. 23 f). The separatedspecimen 58 is moved to a desired position, in this case, to a TEM(Transmission electron Microscope) holder 59 (FIG. 23 g). A depositionfilm for sample fixing 60 is formed in a region that includes theseparated specimen 58 and the TEM holder 59 (FIG. 23 h). The observationregion 50 in this separated specimen 58 is processed into a thin film ofa thickness of approximately 100 nm using the ion beam 52 (FIG. 23 i andFIG. 23 j). The thin film 61 is observed with TEM by transmitting anelectron beam there through.

FIG. 24 is an example of one set of deposition monitor screen of controlsystems used in this embodiment. The operator selects a desireddeposition process from the selection screen, and assigns the scanningregion displayed on the setup screen for a deposition position.Furthermore, its registration screen is the registration screen in FIG.13 with a scanning area newly added.

Fifth Embodiment

FIG. 25 is the loop time dependence of the etching rate and that of theetching rate difference, in accordance with an embodiment of the presentinvention. The etching rate means an etching depth per unit time. Theetching rate difference when the processed region is composed ofmultiple materials is a difference in etching rate between the saidmultiple materials. The probe size d and the optimal dwell time Td forthe preset value of the beam current were also used for selectiveetching, just as the method for depositing a film, as the scan spacingand the dwell time. The etching rate decreases monotonously depending onthe loop time, whereas the etching rate difference takes the maximumvalue at 3 ms. When the loop time is set to this value, the differencein etching between the said multiple materials can be enlargedsubstantially.

FIG. 26 is one set of selective etching monitor screen of controlsystems used in this embodiment. The operator sets the scanning regiondisplayed on the setup screen as a selective etching position, selectsan optical system setting indicating desired etching rate and etchingrate difference from the selection screen. Moreover, two or more choicesare added to the dwell time 72 on the registration screen in FIG. 13.

FIG. 27 is a flowchart showing the selective etching method that is oneof embodiments of this invention. As means for calibrating an etchingrate, the loop time dependence of the etching rate is used. The etchingrate (Y) mostly agrees with Equation 5:

Y=Y _(A)(1−e ^(−P/t))+Y _(N)  (5)

Here, Y_(A) denotes an assist coefficient, P the loop time, τ therelaxation time, and Y_(N) the sputter coefficient. These variables arefound from fitting Equation 5 to the measured values of the etchingrate. Equation 5 is used for calculation of the etching rate and theetching rate difference.

With the use of the means for calibrating the etching rate shown in FIG.26, the probe size d, the assist coefficient Y_(A), the relaxation timeτ, and the sputter coefficient Y_(N) are recorded for each opticalsystem setting (beam current value) and the dwell time Td.Alternatively, a method in which the scanning area, the etching rate,etc., are stored in the form of a table for each optical system settingas substitutes for Y_(A), τ, Y_(N), etc. may be used. In each opticalsystem setting, the scan area S that realizes a desired etching rate isexpressed by Equation 6:

$\begin{matrix}{S = \frac{P\; {a \cdot d^{2}}}{Td}} & (6)\end{matrix}$

Here, Pa denotes the loop time that produces a desired etching ratedifference. The optical system setting that produces a desired etchingrate difference is selected so as to satisfy the scanning area being setby the operator. Thereby, the beam current, the dwell time, and the scanspacing, which are set by the operator in the conventional method, canbe set automatically. Incidentally, since the probe size 14 of the FIB11 affects the etching rate, there is a case where auto-focusing isperformed before selecting an optical system setting and starting filmdeposition.

Other Embodiments

The present invention provides a method for depositing a film on thesurface of a sample by spraying a deposition gas on the surface of thesample and further scanning a focused charged particle beam with acharged-particle-beam irradiation optical system, the method comprisingthe steps of: estimating a deposition rate from information of the scanspacing dependence of the deposition rate; and performing the scanningwhile holding a scan spacing and a dwell time of the charged particlebeam constant.

The present invention also provides a method for selectively etching asample by spraying an etching gas on the sample surface and scanning afocused charged particle beam with a charged-particle-beam irradiationoptical system, wherein an etching rate difference is estimated frominformation of the loop time dependence of the etching rate forconstituent materials, and the scanning is performed while holding ascan spacing and a dwell time of the charged particle beam constant.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

1. A charged particle beam apparatus provided with a function to preparea specimen from a sample comprising: a charged particle beam opticalsystem to irradiate a focused charged particle beam on the sample; aspraying device to spray a deposition gas; a mechanical probe to obtainthe specimen from the sample; and a control unit to control conditionsof the irradiation of the charged particle beam, wherein the controlunit displays a plurality of charged particle beam current valuescorresponding to different deposition rates for the selection ofoperator, and controls a charged particle beam current in accordancewith the selected one of the charged particle beam current values.
 2. Acharged particle beam apparatus according to claim 1, wherein thecontrol unit displays a scanning charged particle beam image byirradiating the focused charged particle beam, and wherein a scanningregion of the focused charged particle beam can be determined by usingthe scanning charged particle beam image.
 3. A charged particle beamapparatus according to claim 1, wherein the charged particle beamoptical system irradiates the focused charged particle beam with thecharged particle beam current to deposit a deposition layer on thesample by using the deposition gas.
 4. A charged particle beam apparatusaccording to claim 1, further comprising: a storage unit to store theplurality of charged particle beam current values, wherein the controlunit displays the plurality of charged particle beam values stored inthe storage unit.
 5. A charged particle beam apparatus according toclaim 2, wherein the control unit calculates each charged particle beamcurrent value from an area of the scanning region.
 6. A charged particlebeam apparatus according to claim 3, wherein the mechanical probeobtains the specimen including the deposition layer.
 7. A chargedparticle beam apparatus provided with a function to prepare a specimenfrom a sample comprising: a charged particle beam optical system toirradiate a focused charged particle beam on the sample; a sprayingdevice to spray a deposition gas; a mechanical probe to obtain thespecimen from the sample; and a control unit to control a beam currentvalue of the focused charged particle beam and displays candidates ofbeam current values, wherein the control unit controls the beam currentin accordance with the beam current value selected form the candidatesand the charged particle beam optical system irradiates the focusedcharged particle beam with the beam current on the sample to deposit adeposition layer on the sample by using the deposition gas.
 8. A chargedparticle beam apparatus according to claim 7, wherein the control unitdisplays a scanning charged particle beam image by irradiating thefocused charged particle beam, and wherein a scanning region of thefocused charged particle beam can be determined by using the scanningcharged particle beam image.
 9. A charged particle beam apparatusaccording to claim 7, further comprising: a storage unit to store thecandidates of beam current values, wherein the control unit displays thecandidates of beam current values stored in the storage unit.
 10. Acharged particle beam apparatus according to claim 8, wherein thecontrol unit calculates each charged particle beam current value from anarea of the scanning region.
 11. A charge particle beam apparatusaccording to claim 7, wherein the mechanical probe obtains the specimenincluding the deposition layer.